This invention relates generally to portable sprayers, and more particularly to an improved gas-charged sprayer for discharging a liquid detergent, or like solution, under moderately high pressures.
Conventional garden sprayers of the stirrup pump-type include a liquid-receiving tank having a dip tube extending to near the bottom of the tank and connected to a flexible hose having a valve-controlled nozzle at its outer end. The stirrup pump forces air into the tank to pressurize the contents. The spray liquid is forced from the tank and out through the spray nozzle. As the level of the liquid in the tank decreases, the pressure of the air above the remaining liquid also decreases, thus making it necessary to repeatedly pump the tank to maintain any sort of uniform pressure within the tank.
More recently, it has been proposed to pressurize sprayer tanks by discharging a liquid or gaseous propellant from a pressurized cartridge or canister into the tank. For example, prior art U.S. Pat. Nos. 3,109,558 issued Nov. 5, 1963 to Yetter and 3,262,609 issued July 26, 1966 to Poitras disclose and teach portable sprayers or spray tanks which are adapted to be charged or pressurized with the well-known propellant, dichlorodifluoromethane, commonly sold under the trademark Freon-12. However, the sprayer apparatus proposed in the aforesaid patents are either overly complicated in their construction, or are otherwise inefficient for their intended use. Thus, in the aforesaid Yetter patent, the liquid Freon propellant is metered by a pressure responsive valve from a supply canister into the spray liquid contained in the sprayer tank where it settles by gravity to the bottom of the tank. While a portion of the liquid propellant at the bottom of the tank vaporizes and percolates as a gas upwardly through the spray liquid to pressurize the ullage of the tank, at least some portion of the liquid propellant residing at the bottom of the tank will be sucked up into the discharge pipe and carried off and wasted each time the sprayer is operated. While the sprayer apparatus of the Poitras Patent eliminates the direct introduction of the liquid propellant into the liquid to be sprayed, it will be noted that in Poitras the propellant supply canister or cartridge positioned wholly within the sprayer tank and occupies space therein which might otherwise be devoted to an increased volume of spray liquid. Also, the Poitras patented sprayer utilizes a comparatively complicated and expensive pressure regulator valve to control the outflow of vaporized propellant from the supply canister into the ullage of the tank.